Name Two solid materials having very low linear expansivity ?

To identify two solid materials with very low linear expansivity, we can refer to the coefficient of linear expansion (α) of different substances. The coefficient of linear expansion represents how much a material expands or contracts in response to a change in temperature.

To find this information, we can consult reliable sources such as physics textbooks or online scientific databases. Here's a step-by-step guide on how you can find this information yourself:

1. Open a web browser and search for a reliable website that provides information on the coefficient of linear expansion for different materials. The National Institute of Standards and Technology (NIST) is a good resource.

2. Once you find a suitable website, browse the available information or use the search function to look for the coefficient of linear expansion values for various materials.

3. Look for materials with low coefficient values. Generally, solid materials with lower coefficients of linear expansion tend to have very low expansivity.

Based on available data, two solid materials often mentioned for their low linear expansivity are:

1. Invar (36% nickel-iron alloy): Invar has an extremely low coefficient of linear expansion, making it nearly insensitive to thermal variations. This characteristic makes Invar ideal for applications where dimensional stability is crucial, such as precision instruments.

2. Borosilicate Glass: Borosilicate glass, commonly known as Pyrex, also exhibits low linear expansivity. It is characterized by its resistance to thermal shock and is commonly used in laboratory glassware, cooking utensils, and scientific apparatus.

Remember, always consult reliable sources and conduct appropriate research to confirm the information and ensure its accuracy.