2.8 物理变化
Section outline
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How do rocks change over time?
::岩石如何随时间变化?These stunning rock arches in Utah were carved by wind-blown sand. Repeated scouring by the sand wore away the rock, bit by tiny bit, like sandpaper on wood. The bits of rock worn away by the sand still contain the same minerals as they did when they were part of the large rock. They have not changed chemically in any way. Only the size and shape of the rock have changed, from a single large rock to millions of tiny bits of rock. Changes in size and shape are physical changes in matter.
::犹他州的这些令人惊叹的岩石拱门是用风吹沙雕刻的。 一再被沙擦擦过岩石,几小块,如木头上的砂纸。 沙擦过的岩石碎片仍然含有与作为大岩石一部分时相同的矿物质。 它们没有任何化学变化。 只有岩石的大小和形状发生了变化, 从一块大岩石到几百万块小岩石。 大小和形状的变化是物质的物理变化。What Is a Physical Change?
::什么是身体变化?A physical change is a change in one or more without any change in chemical properties. In other words, matter doesn’t change into a different substance in a physical change. Examples of physical change include changes in the size or shape of matter. Changes of state—for example, from to or from liquid to gas—are also physical changes. Some of the processes that cause physical changes include cutting, bending, dissolving, , , and . Four examples of physical change are pictured in the Figure .
::物理变化是指一种或多种物质的变化,而化学特性没有任何变化。换句话说,物质在物理变化中不会改变成一种不同的物质。物理变化的例子包括物质大小或形状的变化。状态变化 — — 例如从液体到气体或从液体到气体的变化 — — 也是物理变化。 导致物理变化的一些过程包括切割、弯曲、溶解和。 图中描绘了四个物理变化的例子。Q: In the Figure , what physical changes are occurring?
::问题:在图中,正在发生哪些物理变化?A: The paper is being cut into smaller pieces, which is changing its size and shape. The ice cubes are turning into a puddle of liquid water because they are melting. This is a . The tablet is disappearing in the glass of water because it is dissolving into particles that are too small to see. The lighthouse is becoming coated with ice as ocean spray freezes on its surface. This is another change of state.
::A: 纸正在被切成小块, 它正在改变它的大小和形状。 冰块正因为溶化而变成一整片液态水。 这是 。 平板正在消失在水杯中, 因为它分解成微粒, 微小而看不见。 灯塔正在被冰封着, 正如海洋喷雾在表面冻结一样。 这是国家的另一个变化 。Reversing Physical Changes
::扭转物理变化When matter undergoes physical change, it doesn’t become a different substance. Therefore, some physical changes can be reversed. For example, when liquid water freezes to form ice, it can be changed back to liquid water by heating and melting the ice.
::当物质发生物理变化时,它不会变成一种不同的物质。 因此,一些物理变化是可以逆转的。 比如,当液体水冻结以形成冰时,它可以通过加热和融化冰块而转变为液体水。Q: Salt dissolving in water is a physical change. How could this change be reversed?
::问题:水中的盐溶解是一种物理变化。如何扭转这种变化?A: The salt water could be boiled until the water evaporates, leaving behind the salt. Water vapor from the boiling water could be captured and cooled. The water vapor would condense and change back to liquid water.
::A:盐水可以煮开,直到水蒸发,将盐丢在后面;沸水中的水蒸气可以捕捉和冷却;水蒸气会凝结,并变回液态水。Summary
::摘要-
A physical change in matter is a change in one or more of matter’s physical properties. In a physical change, matter may change its size, shape, or state, but its chemical properties do not change.
::物质的物理变化是物质物理特性的一个或多个变化。 在物质物理变化中,物质可能会改变其大小、形状或状态,但其化学特性不会改变。 -
Because the chemical properties of matter remain the same in a physical change, a physical change is often easy to reverse.
::由于物质化学特性在物理变化中保持不变,物理变化往往很容易逆转。
Review
::回顾-
Define physical change.
::定义物理变化。 -
What are some examples of physical change?
::物理变化的一些例子是什么? -
The wood in the
Figure
is being cut with a chainsaw. Is this a physical change? Why or why not?
::图中的木头是用链锯切开的。 这是物理变化吗? 为什么或为什么?
Explore More
::探索更多Watch the video about physical changes at the following URL. Then answer the questions below.
::在下面的 URL 查看关于物理变化的视频。 然后回答下面的问题 。-
Describe an example of temperature causing a change in the size of matter.
::描述温度导致物质大小变化的例子。 -
How is temperature related to changes in the state of matter?
::温度与物质状态的变化有什么关系?
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A physical change in matter is a change in one or more of matter’s physical properties. In a physical change, matter may change its size, shape, or state, but its chemical properties do not change.
